The obvious polarity difference between the carbon black (CB) and the natural rubber (NR) causes the CB hard to be dispersed in the NR matrix when the addition amount is large. In this paper, polyethylene glycol (PEG) was grafted onto the surface of CB by the liquid phase. The grafted carbon black (GCB) was prepared and applied to reinforce NR. The main physical and mechanical properties of NR were improved because of the better compatibility between GCB and NR. The Mullins effect of the vulcanizate was calculated by the cyclic stress-strain experiment. The results showed that the Mullins effect both existed in the virgin NR system and filled NR system. The degree of Mullins effect was increased with the increase of the filler addition, but that was different for CB and GCB. When the filler addition was below 20 phr, the Mullins effect of NR/GCB was stronger than that of NR/CB. However, when the filler addition was over 30 phr, the Mullins effect of NR/CB was stronger than that of NR/GCB. The Mullins effect was affected by the heat treatment temperature and time. The mechanisms of the Mullins effect were analyzed.
This paper attempted to achieve the purpose of increasing the tensile strength and toughness of polyurethane rubber (PUR) simultaneously by introducing polyethylene glycol (PEG) onto the surface of graphene oxide (GO) to introduce hydrogen bond interactions into the PUR-GO system. GO was grafted with PEG and added to PUR by mechanical blending. The polyethylene glycol-g-graphene oxide (MGO) was characterized by infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and thermogravimetric analysis. The PUR/MGO composites were tested by tensile testing machine, thermogravimetric analysis, dynamic thermal analysis, and scanning electron microscopy. The results demonstrated that PEG was successfully grafted onto the surface of GO and the grafting rate was about 37%. The grated PEG did not affect the crystalline structure of GO. The addition of MGO could improve the thermal stability of PUR vulcanizate. After the addition of GO, the glass transition temperature (Tg) of vulcanizate was shifted to higher temperature. However, the Tg of vulcanizate reinforced by MGO was shifted to lower temperature. The strength and toughness of vulcanizate were significantly improved by adding MGO. The reason was that the hydrogen bond interactions between MGO and PUR were destroyed and the hidden length was released during the strain process. A lot of energy was consumed, and thus the strength and toughness of PUR vulcanizate were improved.
It is still a huge challenge to add a kind of filler into rubber toward strong yet tough elastomer. In this work, a biomimetic design for polyurethane rubber (PUR) by introducing hydrogen bond sacrificial units at the rubber‐graphene oxide interfaces was described. Poly(vinyl alcohol)‐g‐graphene oxide (PGO) reinforced PUR composites were prepared by mechanical blending. The grafting rate of poly(vinyl alcohol) (PVA) on graphene oxide (GO) surface was 23.5%. The improved properties, including the tensile strength, elongation at break and thermal stability of the PUR/PGO composites compared to the virgin PUR vulcanizate were attributed to the hydrogen bonds between PUR and PGO. An 131.2% increase in the tensile strength, a 60.2% increase in the elongation at break and a 23.5°C increase in the maximum decomposition temperature were obtained by adding 1 phr PGO. In addition, the low temperature resistance of the PUR vulcanizate was improved with the addition of PGO. The mechanism of improved properties was attributed to the destruction and reconstitution of hydrogen bond sacrificial units in the PUR/PGO system.
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